2. Related works

The performance of the MAC sublayer in IEEE802.15.4 standard has been evaluated in the literature. The crowd of earlier investigations was based upon MAC sublayer simulation. Lu et al., [24] and Zheng and Lee [25] performed their research based upon simulation.

Gradually, analytical models emerged in this research area where Cao et al., [26] presented an analytical model which was only able to calculate the throughput. Some other models were only able to calculate the energy like [27]. Furthermore, with the passage of time, Markov chain analytical models were proposed, the majority of which are based on [28]'s results.

It should be also pointed out that Bianchi's model [28] was not proper for IEEE802.15.4 standard due to the different functionalities of CSMA/CA mechanism in IEEE 802.11 and IEEE802.15.4 standards.

In [14], although the authors presented an analytical Markov model to evaluate MAC sublayer in the presence of uplink and downlink saturated traffic, the model suffers from the lack of retransmission.

In 2009, despite Yung's efforts to consider retransmission in their proposed model, packet length and acknowledgment were ignored.

In more developed models, Faridi et al., [29] employed retransmission, packet length, and acknowledgment in their advanced model.

In [30], a Markov model is provided to evaluate MAC sublayer and calculate the delay, energy, and throughput which suffers from some drawbacks. Not only did they assume unsaturated data, but they also considered predetermined length for the idle state. In our work, we demonstrate that the duration of the idle states depends on the instantaneous network conditions which might obviously change by passing of time.

Owing to this point, we have considered a variable duration of idle states in our proposed model to deal with the changes in network condition.

In [31], the authors used a model focused on CAP (contention access period), to calculate the throughput and energy and evaluate the effects of a finite length buffer on network performance.

In spite of some drawbacks such as the lack of any queues and some problems in the modeling of the idle states, Park [16, 32] developed the model proposed in [14] through adding retransmission in several investigations. In effect, in Park's model, before passing the whole period of idle states' duration, no node is allowed to leave the idle state, when a new packet is generated. In addition, Park [32] used a backoff with duration of 305 μs instead of the 320 μs, which leads to inaccuracy in his experimental tests. In our experiment, a 1 MHz hardware timer is utilized, to enhance timer resolution up to 1 μs and applying 320 μs to aUnitBackoffPeriod.

In [33], the authors provided different services in Smart Grid by introducing of delay-responsive cross layer (DRX) and also prioritizing input data. DRX classifies information into two categories in the application layer. Potential delay is calculated for every input packet regarding the network history. Then, the best decision was taken at the MAC sublayer to achieve minimum delay to send the packet.

A Reliable Communication Model Based on IEEE802.15.4 for WSANs in Smart Grids DOI: http://dx.doi.org/10.5772/intechopen.84288
